Optical carrier and housing arrangement for receiving a color splitter system and several image converters

ABSTRACT

The invention relates to an optical carrier and housing arrangement to accommodate a color-separation system as well as several image converters, in particular CCD receivers, which is based on a preferably metallic housing block with a radiation entrance opening in one of the side surfaces as well as radiation exit openings in the remaining side surfaces. In the beam path in the interior of the block attachment grooves are provided to fix in position a prefabricatable mirror/filter color-separation system that is accessible from the open cover surface of the block. Wiring-carrier modules support the bare CCD chips and a neccessary drive and evaluation electronics, such that the bare CCD chips make contact face-down above an aperture in the wiring carrier. The modules are adjusted in front of the radiation exit openings in the block and fused into position, so that an electronic correction of the laterally reversed image produced by the mirror/filter color-separation system is achieved by means of the drive and evaluation electronics.

DESCRIPTION

[0001] The invention relates to an optical carrier and housingarrangement to accommodate a color-separation system and several imageconverters, in particular CCD receivers, according to theprecharacterizing clause of claim 1.

[0002] The unexamined German application DE 197 43 526 A1 discloses amultiple-array optics module for a color camera incorporatingencapsulated CCD receivers. This document shows a beam-splitterarrangement in prism form with wavelength-selective mirror layers toseparate the incident radiation into at least three spectral detectionchannels, wherein the CCD receivers are fused to the surfaces of thebeam-splitter arrangement on the side where the light emerges. Theattached sequence of layers comprises three separate individual filters,each with a multilayer combination employing a so-called transfermethod.

[0003] With a camera incorporating such a multiple CCD receiver, theresolution for a given number of pixels can be increased in comparisonto a single-chip camera provided with color filters. That is, eachchromatic-component signal is represented with a resolution thatcorresponds to the full resolving capacity of a CCD black-and-whitereceiver. Another positive aspect is the improved color fidelity andcolor resolution in comparison to single-chip cameras, with asimultaneously increased light sensitivity, which is of considerablemarket relevance in particular for the area of medical technology.

[0004] In multiple-CCD-chip cameras the chromatic separation isperformed by way of a complicated color-separation prism. The chips, asexplained, are fixed either directly to the color-separation prism or tothe inside surfaces of the camera's housing walls, spaced apart from theprism by a slight air gap. In the latter case especially complicatedstructures must be provided for adjustment, so that the manufacturingcosts are considerably higher.

[0005] A tri-color separation system is known from the patent U.S. Pat.No. 5,305,146; it requires a quite complicated arrangement of colorfilters and cylindrical lenses, which causes problems if the aim isminiaturization of the arrangement as a whole.

[0006] In order to reduce the work of assembly during the manufacture ofCCD cameras, according to JP-6-180414 A it was proposed to use as thehousing an arrangement comprising a prefabricated prism block.

[0007] CCD chips contained in a housing are inserted into U-shapedrecesses and, after adjustment as required, are fixed in position byadhesive. The overall dimensions of the arrangement disclosed there arereduced by the depth of the U-shaped recesses, which accommodate thelargest part of the CCD receivers. Integration of parts of the headelectronics and/or drive electronics is not possible according toJP-6-180414 A.

[0008] A direct mechanical connection between CCD chips and the surfaceson the radiation-emitting side of a prism beam-splitter arrangement isdisclosed by JP-5-14910 A, which also specifies that on another side ofthe prism there is additionally provided a wiring carrier withintegrated circuits that comprise parts of the signal preprocessingelectronics.

[0009] According to the unexamined Japanese patent applicationJP-04214521 A it was further proposed to construct a beam splitter onthe basis of coated glass plates that are cast into a transparent blockof resin. For the case in which mirror arrangements are used as beamsplitters, however, the disadvantage arises that image on the CCDreceivers is mirror-reversed, so that optical correction must beundertaken. All the proposed solutions fail to satisfy the demands forhousing arrangements or camera heads that produce a desired degree ofminiaturization. Another disadvantage of using, e.g., CCD componentssituated in dual-inline housings is that the position of thelight-sensitive surface in the housing with respect to the cover glassis subject to error associated with the tolerance required formanufacture and with tilting. These additional sources of error cannotbe eliminated, or can be avoided only by expending considerable effortin assembly and/or adjustment. Given the above considerations, it is theobjective of the invention to disclose an optical carrier and housingarrangement to accommodate a color-separation system as well as severalimage converters, in particular CCD receivers, which can be produced inminiaturized form and enables CCD components that lack housings to beused. Furthermore, the carrier and housing arrangement should beimplementable with low manufacturing costs and enable a large proportionof the subassemblies or components used therein to be prefabricated.

[0010] The objective of the invention is achieved with an opticalcarrier and housing arrangement according to the characteristics givenin claim 1, while the subordinate claims comprise at least advantageousembodiments and further developments.

[0011] The basic idea of the invention consists in starting with ahousing block that is metallic, i.e. conductive and hence capable ofbeing eroded, and incorporates a radiation entrance opening on one ofthe side surfaces as well as radiation exit openings on the remainingside surfaces. Within the path of the beam in the interior of the blockis provided a groove-like recess with appropriate abutment surfaces forfixing in position a mirror/filter color-separation system known per se.The mirror/filter color-separation system can be prefabricated and afteroptical testing is inserted into the corresponding recess or attachmentgrooves in the housing block and fixed there, e.g. by adhesive.

[0012] On wiring-carrier modules provided in accordance with theinvention, which include integrated driving and evaluation electronics,are mounted bare CCD chips, preferably in flip-chip technology. The bareCCD chips are mounted face-down over an aperture in the wiring carrier,so that the light-sensitive surfaces are exposed. The wiring-carriermodules are adjusted in front of the radiation exit openings in theblock and are positioned and fixed there, preferably by fusion to thesubstrate.

[0013] Another approach to achieving the stated objective in accordancewith the invention consists in correcting the laterally reversed imageproduced by the mirror/filter color-separation system electronically bymeans of the integrated drive and evaluation electronics.

[0014] In a preferred embodiment a rigid printed circuit board with CCDdrive electronics is present, which is disposed on the cover surface ofthe block so as to close it off, while flexible connecting sectionsextend away from the rigid board and lead to the wiring-carrier modulesthat contain the bare CCD chips. With such a configuration it ispossible, after the rigid circuit board has been attached to the coversurface of the block, to fold the wiring-carrier modules down by bendingthe flexible sections so that the modules are positioned at the sides infront of the radiation exit openings, and after the appropriateadjustment they are fixed in this position, e.g. by adhesive. In orderto increase the degree of prefabrication and the opportunity forelectrical pretesting, in another preferred embodiment a compositecircuit board is constructed that comprises a central section for theCCD drive electronics as well as at least three sections to accommodatethe bare CCD chips and associated head electronics. Between the centralsection and the sections to receive the CCD chips are formed flexible,electrically conductive regions.

[0015] The composite circuit board can be mounted on a detachablesubframe to facilitate assembly and electrical testing.

[0016] Thus the optical carrier and housing arrangement in accordancewith the invention fulfills the functions of holding the mirror andfilter of the color-separation system, fixing the bare CCD chips inplace, and supporting the CCD drive electronics. The assemblage of CCDchips, chip carrier, drive electronics with housing and color-separationsystem is produced by means of the wiring-carrier module described aboveor by the composite printed circuit board, and is such that variouschip-carrier materials are suitable: ceramic materials as well asplastic films or conventional FR4 circuit-board material.

[0017] The bare chips are arranged to make contact with the carriermaterial face-down by flip-chip technology, e.g. by means of aconductive glue. Both the wiring-carrier modules for the bare CCD chipsand the rigid circuit board with CCD drive electronics can be separatelymanufactured and subjected to the necessary electronic and other tests.

[0018] The accuracy demanded in constructing the necessary openings andapertures in the housing block can be guaranteed by applying thewire-erosion technique.

[0019] In the following the invention is explained in greater detailwith reference to an exemplary embodiment, the description of which isassisted by drawings, wherein

[0020]FIG. 1 shows a plan view as well as side views of the housingblock to accommodate a color-separation system and several imageconverters;

[0021]FIG. 2 is a diagram to show the principles of a wiring-carriermodule for bare CCD chips, in plan and side views; and

[0022]FIG. 3 is a diagram to show the principles of a composite circuitboard, comprising a central section for the CCD drive electronics aswell as at least three sections to accommodate the bare CCD chips andassociated head electronics.

[0023] The housing block 1 shown in FIG. 1 comprises a radiationentrance opening 2 as well as three radiation exit openings 3. In theinterior of the housing block 1 attachment grooves 4 are provided, forfixation of a mirror/filter color-separation system. It is evident fromthe side views that the housing block 1 comprises an open cover surface5 on which are provided attachment bolts 6.

[0024] Of course, additional apertures not shown here can be provided inthe housing block 1 for attaching the block. Furthermore, theprojections 7 in the region of the radiation entrance opening 2 can, forexample, serve for fixation of a camera lens (not shown).

[0025] Apertures 8 in particular in the region of the radiation exitopenings 3 within the housing block 1 serve to accommodate additionaloptical elements, e.g. filters or lenses, depending on the intendedapplication of the entire arrangement and/or on the CCD receiversemployed.

[0026] The wiring-carrier modules 9 in the form of individualprinted-circuit boards, shown in FIG. 2, are used to attach thenecessary electronic components 10 as well as to fix in position thebare CCD chip 11. The chip 11 is fixed in flip-chip technology face-downover an aperture 12 in the wiring-carrier 9 and electrical andmechanical contact are maintained by, e.g., a conductive glue.

[0027] When they have been completed and tested, the wiring-carriermodules 9 are placed in the housing block 1 so that the aperture 12 ofeach module and the bare CCD chip 11 situated there are in front of theassociated radiation exit opening 3, after which they are adjusted andfixed, preferably fused, in position.

[0028] The embodiment according to FIG. 3 is based on a compositecircuit board 13, in which the necessary CCD drive and evaluationelectronics are disposed in a central section 14.

[0029] In addition at least three other sections 15 are provided tocontain the bare CCD chips and associated head electronics, so disposedthat between the central section 14 and the additional sections 15 thereare flexible, electrically conductive regions 17.

[0030] After being detached from a subframe 16, the composite circuitboard so formed can be mounted on the housing block 1 by means of thefixation bolts 6, so that its central section 14 forms a quasi-cover ofthe housing block.

[0031] The additional sections 15 are then folded down in front of theassociated radiation exit openings 3 in the housing block 1, by bendingthe flexible connection regions 17, and after positioning and adjustmentare attached there.

[0032] Because both the head electronics and the drive electronics areintegrated into the system, the necessary adjustment between bare CCDchip and image produced by the color-separation system can be carriedout quasi-online, which results in a reduction of manufacturing costsand shortens the production time.

[0033] The optical carrier and housing arrangement described in terms ofthe present exemplary embodiment, with color-separation system and CCDreceivers as image converters, can preferably be used for miniaturizedmultiple-chip CCD color cameras and in endoscopy, laparoscopy or even inthe intraoral region.

[0034] The housing block itself can be designed as a standard module, ascan the wiring carrier and the composite circuit board, making itpossible to employ bare CCD chips differing in selectivity or otherproperties, but also to use in the housing block differentiatedcolor-separation systems and/or filter combinations, depending on theapplication.

[0035] List of Reference Numerals

[0036]1 Housing block

[0037]2 Radiation entrance opening

[0038]3 Radiation exit opening

[0039]4 Attachment groove

[0040]5 Open cover surface of the housing block 1

[0041]6 Attachment bolt

[0042]7 Projections

[0043]8 Recesses

[0044]9 Wiring-carrier module

[0045]10 Electronic components

[0046]11 Bare CCD chip

[0047]12 Aperture in wiring-carrier module

[0048]13 Composite printed circuit board

[0049]14 Central section

[0050]15 Additional sections

[0051]16 Subframe

[0052]17 Flexible connecting region

1. Optical carrier and housing arrangement to accommodate acolor-separation system as well as several image converters, inparticular CCD receivers, characterized by a preferably metallic housingblock with a radiation entrance opening in one of the side surfaces aswell as radiation exit openings in the remaining side surfaces, suchthat in the beam path in the interior of the block attachment groovesare provided to fix in position a mirror/filter color-separation systemaccessible from the open cover surface of the block; wiring-carriermodules for bare CCD chips as well as drive and evaluation electronics,wherein the bare CCD chips make contact face-down above an associatedaperture in the wiring carrier, and the modules are adjusted in front ofthe radiation exit openings in the block and fused into position; andelectronic correction of the laterally reversed image produced by themirror/filter color-separation system, by means of the drive andevaluation electronics.
 2. Arrangement according to claim 1,characterized in that a rigid printed-circuit board with CCD-driveelectronics is fixed to the cover surface of the block so as to closethe block off, such that by way of flexible sections the rigid circuitboard is connected to several wiring-carrier modules that contain bareCCD chips and are folded down at the sides, each then being adjusted infront of the associated radiation exit opening and fixed there,preferably by means of adhesive.
 3. Arrangement according to claim 2,characterized by a composite circuit board comprising a central sectionfor the CCD-drive electronics as well as at least three sections tosupport the bare CCD chips and associated head electronics, such thatbetween the central section and the conductive sections to support theCCD chips flexible, electrically conductive regions are formed. 4.Arrangement according to claim 3, characterized in that the compositecircuit board is mounted on a detachable subframe to facilitate assemblyand electrical testing.
 5. Arrangement according to one of the precedingclaims, characterized by its application for miniaturized multiple-chipCCD color cameras.